This invention relates to force limiting means for use with electromechanical transducers and more particularly to a force limiting means capable of stopping a transducer to prevent breakage of the same relatively independent of the direction of the applied force.
This invention involves improvement in force limiting mechanisms for relatively small transducers of the cantilever beam configuration.
U.S. Pat. No. 3,970,982 entitled BEAM TYPE TRANSDUCERS EMPLOYING ACCURATE INTEGRAL FORCE LIMITING issued on July 20, 1976 patented and assigned to the Assignee herein, shows cantilever transducers. In that patent, a detailed description of the problems one experiences in controlling excessive forces applied to the relatively fragile units was presented. One solution depicted apparatus wherein a silicon member utilized as a diaphragm had a central shallow depression formed on a surface thereof. A glass cover member had a central aperture and is coupled to the silicon member to cover the depression. A push rod was inserted in the aperture of the glass and secured to the silicon diaphragm. Hence, when an excessive force was imparted to the silicon diaphragm, the silicon coacted with the glass to stop the diaphragm for all forces which exceeded a predetermined level. The impingement of the thin silicon diaphragm with the glass cover member stops the silicon diaphragm without fracturing or rupturing of the same.
Since the shallow depression in the silicon could be accurately and reliably controlled, one was further assured that the elastic limits of the transducer would not be exceeded.
The stop or limiting apparatus described in the above noted application operates to prevent forces applied in the positive direction (i.e. relatively transverse to the diaphragm) from fracturing or rupturing the diaphragm or from exceeding the elastic limits of the cantilever transducer coupled to the diaphragm by means of the push rod.
However, it is also important to stop and prevent rupture or fracture of the assembly for forces applied in an opposite direction to the desired direction. These forces may develop, for example, when the apparatus is mishandled, dropped, or exposed to a high negative pressure.
It is therefore an object of the present invention to provide improved dual direction stopping mechanisms for a push rod cantilever transducer.